WACO, Texas (AP) — Texas law enforcement officials on Friday launched a criminal investigation into the massive fertilizer plant explosion that killed 14 people last month, after weeks of largely treating the blast as an industrial accident.

The announcement came the same day federal agents said they found bomb-making materials belonging to a paramedic who helped evacuate residents the night of the explosion. Bryce Reed was arrested early Friday on a charge of possessing a destructive device, but law enforcement officials said they had not linked the charge to the April 17 fire and blast at West Fertilizer Co.

“It is important to emphasize that at this point, no evidence has been uncovered to indicate any connection to the events surrounding the fire and subsequent explosion ... and the arrest of Bryce Reed by the ATF,” the McLennan County Sheriff’s Office said in a statement.

Texas Department of Public Safety said earlier Friday that the agency had instructed the Texas Rangers and the sheriff’s department to conduct a criminal probe into the explosion. The agencies will join the State Fire Marshall’s Office and the Bureau of Alcohol, Tobacco, Firearms and Explosives, which have been leading the investigation and never ruled out that a crime may have been committed.

“This disaster has severely impacted the community of West, and we want to ensure that no stone goes unturned and that all the facts related to this incident are uncovered,” DPS Director Steven McCraw said.

McLennan County Sheriff Parnell McNamara said residents “must have confidence that this incident has been looked at from every angle and professionally handled — they deserve nothing less.”

The statement did not detail any further reasons for the criminal investigation and said no additional information would be released.

Reed, meanwhile, was in federal custody. A criminal complaint unsealed Friday afternoon said he was arrested after McLennan County deputies were called earlier this week to a home in Abbott, a town about five miles from West, and found bomb-making materials — including a galvanized metal pipe, canisters filled with fuses, a lighter, a digital scale and a variety of chemical powders.

“After further investigation, it was determined that the resident had unwittingly taken possession of the components from Reed on April 26,” says the complaint signed by ATF special agent Douglas Kunze.

An ATF explosives specialist and a chemist examined the items and agreed the “combination of parts can be readily assembled into a destructive device,” the complaint says.

Reed made an initial appearance in federal court in Waco on Friday, but did not enter a plea.

Officials have largely treated the West explosion as an industrial accident, though investigators still searching for the cause of a fire that preceded the blast have said they would treat the area as a crime scene until all possibilities were considered.

The State Fire Marshal’s Office released a statement Friday saying it decided to continue pursuing a criminal probe because roughly 250 leads have developed and more than 400 people have been interviewed.

Authorities have focused on ammonium nitrate, a chemical commonly used as a fertilizer, but that also can be explosive in the right conditions, as the cause of the explosion.

Reed was one of several paramedics who helped evacuate residents from nearby apartments after the fire erupted and shortly before the explosion. He has spoken to The Associated Press extensively, and said he was devastated by the explosion, which he said killed one of his closest friends, Cyrus Reed. Bryce Reed eulogized the firefighter at his funeral; the two are not related.

Bryce Reed was working as a West paramedic the night of the explosion, but he was “let go” two days later, according to an email that a regional EMS group sent to the Texas Department of State Health Services. The email, obtained by the AP under Texas’ open-records law, included no other details.

Bryce Reed’s wife, Brittany Reed, declined to comment early Friday.

“I can’t. No comment, no comment, no comment right now,” she said before hanging up the phone.

Crystal LeDane, who lives down the street from Reed, said he was a good neighbor who had changed her flat tire and would sometimes give medical advice about her children’s minor injuries.

“I’ve been thinking it’s an accident, and I still believe that until there’s more information,” said LeDane, as neighbors stood outside Reed’s red brick duplex.